The invention relates to a device for converting circularly oscillating electromagnetic radiation beams into linearly oscillating radiation beams.
Some transmitters used in satellite transmission technology emit linearly polarized radiation beams, whereas others emit circularly polarized radiation beams. The radiation beam of a transmitter emitting linearly oscillating radiation beams can be converted from a horizontally extending oscillation beam into a vertically extending oscillation beam, and vice versa from a vertically extending radiation beam into a horizontally extending radiation beams using an oscillation mode converter (OMT), so that the received radiation beam can be oriented to match the antenna characteristic.
Difficulties arise with radiation beams having a circular oscillation, which can only be received by antennas capable of receiving circularly oscillating radiation beams. A conversion of a circularly oscillating radiation beam into a radiation beams that can be received by an antenna adapted for linearly oscillating radiation beams has not been possible hereto.
It is therefore an object of the present invention to provide an apparatus which can allows circularly oscillating radiation beams to be received by antennas that are adapted to receive linearly oscillating radiation beams.
This object is solved by the invention in that a depolarizer is supported in an oscillation converter for rotation between a vertical output for vertically oscillating radiation beams and a horizontal output for horizontally oscillating radiation beams, and that between the horizontal output and the vertical output a depolarization position for circularly oscillating radiation beams is provided, in which depending on the rotation direction of the depolarizer radiation, a beam performing a left-handed oscillation can be supplied either to the horizontal output or the vertical output and a radiation beam performing a right-handed oscillation can be supplied either to the vertical output or the horizontal output.
In this way, linearly oscillating radiation beams can appear at the respective outputs of the oscillation converter, regardless if a linearly or circularly oscillating radiation beam is supplied to the oscillation converter. The device can output either horizontally or vertically oscillating radiation beams depending on the antenna design. Accordingly, antennas adapted for receiving linearly oscillating radiation beams can always be used for receiving the radiation beams, independent of the respective radiation beam source.
According to a preferred embodiment of the invention, the depolarization position for circularly oscillating radiation beams is at an angle of 45xc2x0 relative to both the horizontal and the vertical direction. By selecting a 45xc2x0 angle, the received energy of the circularly oscillating radiation beams can be optimized.
According to another preferred embodiment of the invention, a motor drive is provided for rotating the depolarizer. Advantageously, the drives are implemented as electric drives which can be easily controlled.
According to another preferred embodiment of the invention, the motor drive includes a controller that relies on the oscillation direction of the incident radiation beams. With this controller, the depolarizer can be automatically rotated independent of the oscillation direction of the incident radiation beams. By rotating the depolarizer, the orientation of the depolarizer inside the oscillation converter can be adjusted so that the radiation beams exiting the oscillation converter have the desired oscillation direction.
According to another preferred embodiment of the invention, the depolarizer has depolarizing elements which are oriented vertically to match a vertical oscillation of the incident radiation beams. With this design, vertically oscillating radiation beams exits the oscillation converter without conversion. A horizontally oscillating radiation beam can be treated in an analogous manner.
According to another preferred embodiment of the invention, for a circular oscillation of the incident radiation beams, the depolarizing elements are oriented at an angle of 45xc2x0 with respect to both the horizontal and the vertical direction. With this orientation of the depolarizer, either the horizontal or the vertical component of the incident radiation beams exits the oscillation converter.
According to another preferred embodiment of the invention, the depolarizing elements of the depolarizer can be rotated from the vertical direction towards the horizontal direction by 45xc2x0 for obtaining horizontally oscillating radiation beams from circularly oscillating radiation beams. By rotating the depolarizing elements from the vertical direction into the horizontal direction in this manner, the oscillation converter is able to convert centrally oscillating radiation beams into horizontally oscillating radiation beams.
According to another preferred embodiment of the invention, the depolarizing elements of the depolarizer can be rotated from the horizontal direction towards the vertical direction by 45xc2x0 for obtaining vertically oscillating radiation beams. In this position, the circularly oscillating radiation beams exit the converter predominantly as radiation beams oscillating in the vertical direction.